Editor in Chief
The electronics industry’s move away from using solders containing lead is setting up a clash between private industry and the U.S. military that may well lead to the end of the COTS era as we have come to know it.
COTS, of course, refers to commercial-off-the-shelf components, subsystems, and software that over the past decade have become the foundation of most military and aerospace electronic and opto-electronic integrated systems.
Among the benefits of COTS are affordability, broad availability, and the potential for rapid technology upgrades. Off-the-shelf, open-systems hardware and software are the rule now, and the rare exception is the custom-designed system built specifically to military specifications.
We soon may start seeing a change in this now-familiar COTS approach, however. The reason involves the Reduction of Hazardous Substances rules-better known as RoHS-which are pressuring electronics manufacturers to phase out their use of leaded solders in attempts to eliminate substances like lead from the environment where it can cause harm to humans.
RoHS takes effect this month in Europe, and other lead-free requirements are pending throughout the world. No company whose leaders want to continue selling into the lucrative European electronics market will keep using leaded solders on a large-scale basis. As a result, the electronics industry throughout the world is defaulting to nonlead solders.
The catch, however, is that nonlead solders simply don’t work for the military, where system reliability is an imperative, not an option.
Lead-free solders, which RoHS mandate, tend to grow tin whiskers, which are physical abnormalities that form in nonlead solders. These tin whiskers can lead to unpredictable short circuiting and failures of electronic parts. These growths are electrically conductive, can grow in days or years, and can easily bridge between contacts, can touch each other to cause electrical problems, and can break off to bridge board traces and foul optics.
This phenomenon will compromise the reliability and reputation of most, if not all, COTS electronic parts and subsystems, and the military simply cannot abide this level of reliability; missions and lives depend on electronics that always work when fighting forces need them.
The military, meanwhile, has no effective and accepted tests to determine the susceptibility of platings to whiskering. Furthermore, no mitigation techniques exist to guarantee reliability levels that the Defense Department requires for high-reliability systems.
The only sure-fire way to ensure military-level electronics reliability is to add at least 3 percent lead to the tin-based solder, and this violates RoHS rules.
The military’s short-term solution is to stay with leaded solder, at least for the foreseeable future. It is this policy that forms the threat to COTS as we know it. The commercial electronics industry is moving away from lead solder, and the military is staying put. With each passing day the two sides put more distance between each other.
Military leaders have no plans simply to settle for lead-free solder. They want to know for certain how lead-free solder influences system failure rates, and program managers will demand documented proof before they will accept lead-free solder. Today, no quantifiable means of predicting tin-whisker-related problems exist.
If no such data is available, then custom soldering with leaded compounds may be the only alternative. If the military persists in banning lead-free solders, and there are few alternatives on the commercial market, the military must resort to custom soldering solutions.
Inevitably, this alternative will prove to be expensive, slow, and inflexible. It promises to have many-if not all-of the drawbacks of the pre-COTS days before 1994 when everything the military bought was a custom design.
In light of these developments, it might make sense for small electronics shops to start gearing up to provide leaded solder for military applications.
I can see a whole new business line for electronics manufacturers to knock off the lead-free solder balls from ball-grid-array devices and replace them with leaded solder. Entire boards may need to be reflowed with leaded solder, and small companies are bound to step forward with such services.
The ability to transform components built with lead-free solder into devices with leaded solder, for some, may promise to be a lucrative business opportunity-at least in the short term.
The biggest problem for the military most likely will not be a lack of suppliers of lead solder services. If there’s a need, then a supplier base will appear. The big problem will likely be high costs and unpredictable availability-the same problems that COTS was intended to solve.
